wpr_simulation2/demo_cpp/5_lidar_data.cpp

#include <rclcpp/rclcpp.hpp>
#include <sensor_msgs/msg/laser_scan.hpp>

std::shared_ptr<rclcpp::Node> node;

void LidarCallback(const sensor_msgs::msg::LaserScan::SharedPtr msg)
{
    int nNum = msg->ranges.size();
    
    int nMid = nNum / 2;
    float fMidDist = msg->ranges[nMid];
    RCLCPP_INFO(node->get_logger(), "ranges[%d] = %f m", nMid, fMidDist);
}

int main(int argc, char** argv)
{
    rclcpp::init(argc, argv);

    node = std::make_shared<rclcpp::Node>("lidar_data_node");

    auto lidar_sub = node->create_subscription<sensor_msgs::msg::LaserScan>("/scan", 10, LidarCallback);

    rclcpp::spin(node);

    rclcpp::shutdown();

    return 0;
}